The present invention relates to a plasma processing apparatus for processing an object to be processed (process object) by using plasma.
In processing a process object especially an insulating film by utilizing plasma, a parallel-planar plasma processing apparatus, for example, has hitherto been used in which different two radio frequencies (RF""s) are applied to opposing electrodes (prior art 1). A plasma processing apparatus having a permanent magnet disposed in ring-form arrangement on the back of a RF electrode is disclosed in, for example, JP-A-8-288096 (prior art 2). A plasma processing apparatus, in which a planar antenna member is so disposed as to oppose an electrode carrying an object to be processed, the antenna member being supplied with a xcexc wave and a slit opening is formed in a front surface of the planar antenna, is described in, for example, JP-A-9-63793 (prior art 3). An etching apparatus using a high frequency in UHF band, in which an earth structure on the top of an antenna is concave, is disclosed in, for example, JP-A-11-354502 (prior art 4). Further, a parallel-planar UHF plasma apparatus in which a high frequency in UHF band is supplied to a disk-shaped antenna by a coaxial cable and the antenna diameter is set to a predetermined value n/2xc2x7xcex (n: integer) is disclosed in, for example, JP-A-10-134995 (prior art 5).
Prior art 1 lacks plasma distribution control means and hence, when the kind of gas and the pressure are changed, distribution of radical compositions and that of reaction products change, making it sometimes difficult to make the processing distribution uniform. In addition, plasma is difficult to increase in density and the processing speed (etching rate) is slow.
In prior art 2, the permanent magnet is used and as a result, a magnetic field is formed locally at a site nearly limited to the size of the permanent magnet. When the trapping effect due to the magnetic field is desired to be increased, the intensity of the magnetic field increases near the magnet and the plasma density becomes high at that portion. Further, a bias is applied to the RF electrode to draw ions and as a result, sputtering takes place locally, raising a problem that local wear of the electrode is caused to increase foreign matters and decrease the reliability of the apparatus. For the magnetic field formed at that portion, compatibility between local improvement and distribution controllability is difficult to achieve.
In prior art 3, the slit is formed in the antenna and the length of the slit is set to about xc2xd to {fraction (1/10)} of xcex (xcex:a wavelength of xcexc wave in the tube) to adjust the distribution but it is difficult to adjust the radiation of xcex wave and the electric field distribution.
Prior art 4 pertains to the earth structure on the top of an antenna for avoidance of concentration of electric field. Even if the earth structure is made to be concave, difficulties still remain in making the electric field distribution per se uniform and adjustment of the distribution is difficult to achieve when gas, pressure or power is changed.
In prior art 5, since the antenna center corresponds to the maximum amplitude of electric field and the antenna edge corresponds to the node of electric field, the electric field distribution directly below the antenna always becomes convex. Consequently, it is difficult to make plasma uniform.
Accordingly, an object of the present invention is provide, in a method of generating plasma by using a high frequency in VHF or UHF band and a magnetic field, a plasma processing apparatus which can realize the generation of plasma of high density and high uniformity in a wide parameter region.
To accomplish the above object, according to one aspect of the invention, a plasma processing apparatus comprises a vacuum vessel, a processing chamber arranged in the vacuum vessel and supplied with gas, a support electrode arranged in the processing chamber to support an object to be processed, high frequency admitting means including a disk-shaped antenna for supplying a high frequency in UHF or VHF band to the processing chamber and an emitting port arranged laterally of the antenna and formed of an insulating member, and magnetic field forming means for forming a magnetic field in the processing chamber, wherein in the high frequency admitting means, the ratio between the radius of the antenna and the effective length of the emitting port is 0.4 or more and 1.5 or less. The effective length d* of emitting port referred to herein is given by d*=(f/f0) d/∈rxc2xd where the real size of the emitting port is d, the specific inductivity of the insulating member constituting the emitting port is ∈r, the frequency used is f and the reference frequency f0 is 450 MHz.
Where the high frequency has a wavelength of xcex0 in vacuum, the radius of the antenna is preferably xcex0/4 or less. Preferably, a surface of the antenna opposing the processing chamber is made of Si, SiC or C. Preferably, part of the emitting port is closed with a metal plate to restrict the size of the emitting port approximately to a wafer diameter to be processed. Further, the antenna is formed with a slit opening (openings), a planar member made of Si, SiC or C is arranged on the surface of antenna adjoining plasma and the high frequency is supplied to the processing chamber through the planar member.
Other objects, features and advantages of the present invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.